Users of indicia reading apparatuses such as bar code reading apparatuses have always rated as an important factor in determining overall satisfaction with an apparatus the “snappiness” of operation—how fast a decoded message is output after reading is initiated. The time to output a decoded message after receipt of a trigger signal can be referred to as the trigger-to-read (TTR) time.
In order achieve snappiness of operation, designers of reading apparatuses have implemented designs wherein several frames of image data are captured and subjected to processing in succession one after another over a short time period. If processing of a first frame to be subject to a decode attempt fails, another captured frame is processed, and then another until an indicia is successfully decoded. While a succession of frames are being captured and subject to decoding, a user may be moving the apparatus (which may be hand held) into a position wherein a higher quality image may be captured.
Providing an apparatus which repeatedly captures and attempts to decode images has significant advantages. However, challenges continue to be noted with presently available indicia reading apparatuses. Some of the challenges faced by designers of indicia reading apparatuses have been imposed by technological advances.
For example, with advances made in circuitry and software design, including those by the assignee Hand Held Products, Inc. reading apparatuses are now capable of reading indicia formed on substrates at increasingly long range reading distances. At longer reading distances, fewer light rays projected by an on board lighting assembly of a reading apparatus (where present) are able to reach and be reflected from a target substrate. Because of the increased depth of field available with currently available reading apparatuses such as the IT4XXX imaging module, poor illumination reading conditions are more commonly encountered. For battery conservation purposes and for cost purposes, it has been a goal of designers or reading apparatuses to decode indicia such as bar codes with little even no artificial illumination.
In addition, with respect to image sensor based reading apparatuses, image sensors continue to grow in density. Fabrication technologies exists for making high density (e.g., million plus pixel) image sensors at low cost. Such image sensors generate more image data, which consumes additional processing time.
There remains a need to read bar codes and other decodable indicia quickly in normal operating conditions and in an expanding range of operating conditions.